Known medicated shampoos are, for example, the ketoconazole shampoos which are marketed in a 2% formulation and which show a beneficial effect in dandruff and seborrheic dermatitis after topical application. Ketoconazole was disclosed by Rosenberg et al. in U.S. Pat. No. 4,569,935 to be useful in the topical treatment of psoriasis and seborrheic dermatitis. Ketoconazole shampoos that exhibit better cosmetic attributes such as lathering and conditioning, and are acceptably stable to degradation so that they can be formulated to contain less than 2% active ingredient are disclosed in U.S. Pat. No. 5,456,851. Elubiol shampoos having a skin grease regulating action are known from WO-93/18743. Some anti-dandruff formulations contain coal tar, selenium sulfide or a pyrithione salt, e.g. zinc or sodium pyrithione as an active agent. WO-96/29045 generically discloses combinations of such a cytotoxic agent and an antifungal agent for the treatment of seborrheic dermatitis of the scalp; specifically disclosed is the combined use of an unidentified composition comprising 1.8% coal tar and an unidentified solution comprising 2% ketoconazole. WO-96/29983 discloses mild aqueous detergent compositions comprising from about 4 to about 12% by weight of an anionic surfactant, an amphoteric surfactant at a level of at least about 0.75 parts by weight per part by weight of said anionic surfactant, and one or more of 11 listed therapeutic agents.
U.S. Pat. No. 4,209,449 (EP-0,013,713) discloses synthetic, amphotheric phospholipids which exhibit outstanding foaming, viscosity-building, wetting, cleansing, detergency, anti-static and emulsifying properties. A number of the synthetic, amphotheric phospholipids described therein are commercially available from Mona Industries, Inc., Paterson, N.J., USA under the name Phospholipid PTC (cocamidopropyl phosphatidyl PG-dimonium chloride), Phospholipid EFA (linoleamidopropyl phosphatidyl PG-dimonium chloride), Phospholipid PTS (stearamidopropyl phosphatidyl PG-dimonium chloride).
Prior art shampoos comprising anti-dandruff agents are designed in such a way that an optimum balance is achieved between efficacy and tolerability; the concentration of the active ingredient in the medicated shampoos is such that as many users as possible are effectively treated and as few as possible suffer adverse effects. Nonetheless, there remain substantial numbers of patients who do not benefit from using prior art shampoos, either because they do not respond to the treatment, or worse, because they do not tolerate the treatment with a particular medicated shampoo.
The number of patients not responding to particular medicated shampoo can be quite high (ketoconazole up to 30% ; selenium sulfide up to 40%). Consequently, there is a hard felt need for new shampoos which provide effective anti-dandruff treatment for a larger proportion of number of patients using such a new shampoo; i.e. a new shampoo for which there are fewer non-respondents than with prior art shampoos.
On the other hand, patients suffering from dandruff or seborrheic dermatitis, as well as the authorities approving medicated shampoos, apply increasingly stricter criteria which such shampoos should meet. Amongst these criteria the most important are: absence of further aggravation of the condition due to the treatment, lowest possible incidence of side effects, further increase in the absence of symptoms such as irritation, pruritus and scaling (both adherent and loose scaling); improved cosmetic acceptability, in particular, good cleansing properties, absence of odour or stench, absence of staining or soiling of the clothes, and overall conditioning (wet and dry combing properties). Dandruff or seborrheic dermatitis are often accompanied by high or excessive oil or sebum production, and compositions having a beneficial effect thereon would clearly constitute a further advance in the treatment of dandruff.
Thus far, in order to achieve the above desiderata, most efforts have involved reformulating the shampoo base. There is, however, still a need for increasing the tolerability/acceptability of medicated shampoos, i.e. new shampoos are desired that are tolerated better by larger proportions of patients using such new shampoos.